The present invention relates to a clock source design, and more particularly, to an oscillator circuit with a reconfigurable oscillator amplifier and/or a hybrid amplitude calibration circuit and an associated method.
A reference clock is generally required in a variety of circuits. For example, a clock source may be realized by a crystal oscillator for providing a required reference clock, where a quartz crystal resonator used in the crystal oscillator operates like a resonant circuit that is tuned to a selected resonant frequency. In order to initiate and maintain strain on the quartz crystal resonator, the crystal oscillator includes an oscillator amplifier coupled across nodes of the crystal. The crystal oscillator may be required to operate under different modes to generate the reference clock for different system scenarios. In addition, amplitude calibration may be required to control the oscillation amplitude for achieving good noise performance of the crystal oscillator output when there is a mode transition from a current operation mode to a next operation mode. Thus, there is a need for an innovative oscillator amplifier design capable of supporting different operation modes and/or an innovative amplitude calibration design with quick settling, low power and high performance.